The present invention concerns a method of removing a metal sleeve from a bore and to a device for the same. More particularly, but not exclusively, this invention concerns a method of removing a metal sleeve from a bore in an aircraft structure, the sleeve being secured within the bore by means of an interference fit, especially by means of a cold-worked sleeve-expansion method. The invention also concerns a method of replacing a fixing received within a sleeve and a device for removing a metal sleeve from a bore.
When fixing elements together with a bolt or other fixing that passes through a bore through the elements, particularly when the elements are made of differing materials, it is common to provide a sleeve, for example in the form of a bushing or a bearing arrangement, to line the bore within one or more of the elements. One method of securing the sleeve within the bore is to insert the sleeve in the bore and then cold expand the sleeve within the bore. Such a technique is utilised in the GromEx™ system provided by “FTI” (Fatigue Technology, Inc of Seattle, USA). Briefly, a sleeve received in a bore in a part is expanded by means of a hydraulic puller unit (for example the “Big Brute” Puller—Part No. 2720-008, also from FTI), which exerts a pulling force that pulls a mandrel through the sleeve, whilst the puller unit reacts at least some of the pulling force by means of a nose cap of the unit that butts against the surface of the part that defines the bore. A bolt may then be accommodated within the sleeve to fix the part to another element or part. In some cases, the bolt may form a friction fit or an interference fit with the sleeve.
If a bolt received in such a sleeve is damaged with consequent wear or damage to the sleeve then it is desirable to be able to remove the sleeve from the bore without causing damage to the surrounding material such that a replacement sleeve and bolt may be inserted into the bore. In some circumstances it is possible to remove both the bolt and sleeve simultaneously. In other cases, where the bolt and sleeve are more securely fitted in the bore, it may be better to remove the sleeve and bolt one at a time. In such cases, the bolt may often be readily removed by conventional pulling or pushing units that are able to exert sufficient forces (often in excess of 10 kN in some, for example aerospace, applications). The sleeve may then be removed, but the force required may prove to be higher, for example greater than 50 kN in some applications. It has been found that in certain circumstances the force required to remove a sleeve is too high to be practical to use the methods employed with existing equipment. Examples of such circumstances include, for example, attempting to remove long sleeves or attempting to remove sleeves that have been expanded in a bore that extends through multiple elements, each made from a different material having a different hardness.
The present invention seeks to mitigate the above-mentioned problem(s). Alternatively or additionally, the present invention seeks to provide an improved method of removing a metal sleeve from a bore, the sleeve being secured within the bore by means of an interference fit.